Introduction to MIDI and Computer Music: Reason: Filters and EQ
Earlier this term, we studied some basic acoustics concepts — for example, that single complex sounds actually are made up of many different frequencies. These frequencies are called the spectrum of that sound (see Acoustics 1 app and Acoustics 2 app). A sound’s particular spectrum is one of the main factors that determines its tone quality and sound color. Generally speaking, a brighter, harsher sound includes more high frequencies, while a more mellow sound has fewer high frequencies.
We experimented with different methods that alter a SubTractor patch’s spectrum:
When composing or arranging electronic music, it’s often helpful to alter the frequency spectrum of a sound or track. There are many reasons to do this, for example:
There are several standard EQ types, and these are built into the Reason Main Mixer, in the EQ section. These are all called parametric EQs, because you can change the cutoff or center frequency parameter of the filters, among other parameters. There are knobs to control the parameters, but it is more instructive to manipulate the parameters directly on a filter frequency response graph in the Spectrum EQ window. To see this window, press the button, in the mixer EQ section, circled in red below.
What you see is a graph of frequency, on the horizontal axis, and the amount of cut or boost that the EQ performs on the input sound, shown in dB on the vertical axis. If the Analyzer box is checked, you will see a real-time 2D spectrogram displayed “behind” the filter graph, showing the effect on the spectrum of any EQ that is active.
Here is a brief description of the standard EQ types.
Note that you must check the LPF (low-pass filter) box to see and change the filter.
Notice that you can have the LPF and HPF active at the same time. The result is the intersection of the two filter shapes.
To enable the peak/notch EQs, check the EQ On box. If you already have low-shelf or high-shelf EQ settings that are not flat (that is, a gain of zero), then command-click their handles to set their gains to zero. Now you can see the effect of the peak/notch EQs more easily.
To change the Q, or width of the peak or notch shape, option-drag the blue or green handles, dragging horizontally or vertically.
To get a more narrow bell-curve shape, check the E Mode box. This sets a constant Q that does not depend on the gain of the filter. But the main thing is that this lets you make the bell curve narrower.
Check the HF Bell or LF Bell boxes to turn the shelf EQs into peak/notch EQs, albeit without adjustable Q.
Notice that as you manipulate the controls on the Spectrum EQ graph, the EQ knobs and switches in the Main Mixer channel strip change accordingly.
There are other parametric EQs available in Reason: the standalone PEQ-2 Two Band Parametric EQ and the MClass Equalizer. Given what you know about the EQs in the Main Mixer, you should be able to figure out these devices.
There is also a graphic EQ built into the BV512 Digital Vocoder. A graphic EQ gives you a number of fixed frequency bands spread across the spectrum, using equal musical intervals, such as octaves or major thirds. You can boost or cut each band. To get the graphic EQ behavior from the BV512, set the Equalizer/Vocoder knob to Equalizer, and select the number of bands using the knob above. The Shift knob to the right of the display shifts all the frequency bands lower or higher by an octave.